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Review: NwAvGuy's O2 DIY Amplifier

Discussion in 'Sound Science' started by shike, Aug 25, 2011.
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  1. upstateguy
    Why doesn't someone start another NwAvGuy's O2 DIY Amplifier thread in the amp forum, so we can pick up where we left off
  2. zzffnn
             I used to own both Objective2 amp and Hifiman HM-801 (stock discrete amp card) at the same time. I did some careful comparison. I eventually sold the HM801 and now live happily with O2. Please read on and see why.
            Comparing HM801 vs iPhone 3GS -> O2 amp:
            1) From LCD-2 r1s
    My ears prefer the O2 rig slightly. HM801 sounds more veiled and lacks transparency, although its large soundstage is appreciated. I do prefer slightly warm and laid-back sound in general, however HM801 with LCD2 r1s are too warm / laid-back for most of my music listening. The O2 rig provides more realism, dynamic contrast and resolution, although the perceived soundstage depth is slightly less.
             2) From Westone ES3Xs
    My ears CLEARLY prefer the O2 rig. With HM801 (and in comparison with O2 rig), bass sounded loose, treble was too laid-back and transparency is lacking. Even though HM801 is more portable, I still found myself turning more to the O2 rig.
             3) From DT880/600ohms
    I slightly prefer HM801, which added warmth to DT880s. DT880s are slightly bright to my ears, so they welcome the warmth added by HM801 to bass and mid range, along with slight reduction in treble. I can understand it if a detail freak would prefer O2 with DT880s though, because everything there is crystal clear and bass is fast and tight along with good impact. 
            4) MarkL damped Creative Aurvana Live or V-MODA V80
    Not too much difference really. I can live with either rig happily.
           So in summary, HM801 does not worth $400 more for me (I would rather put that extra $400 into desktop rig). Neither rig sounds as good as my AMB Gamma2 coupled with Beta22 and neither rig is truly portable. As a transportable rig, O2 amp attached to iPhone 3GS or Sansa Clip is slightly larger in size than HM801, but offer similar or better performance for much less money.
           Note: All impressions herein were obtained with volume matched to average of 82 db (except for Westone ES3Xs, wherein I volume-matched by ear).
  3. peanuthead
    Did you just volunteer? :wink:

  4. upstateguy


    I would like to hear more about that comparison.
  5. zzffnn
           @ upstateguy
          I am not sure comparing AMB Beta22 with Objective2 is fair, in view of the difference in size, part cost/quality and power supply.  However, since you asked for it, here it is.
         Overall Beta22 provides better musical immersion, soundstage depth (O2 is more upfront in presentation) and dynamic contrast.  
          In bass region, Beta22 hits noticeably harder and deeper than O2. Speed, tightness, and resolution is about on par.
          In mid region, they are on par. Music may sound slightly closer to you with O2, which maybe a good thing if you want a more forwarded presentation (in comparison sense, as neither is overly forward).
          In treble region, Beta22 sounds noticeably more laid-back (but still clear/clean enough for my ears). O2 let you hear treble more closely when you are analyzing or monitoring. When using some bright headphones such as DT880s or K701s, I would prefer Beta22 over O2. If you have some music that sounds aggressive and trebly, Beta22 may work better. If your music sounds too distant for you to start with, I would suggest using O2.   
         To my ears, Beta22 is worth the difference in cost. If I do not need portability, I would always use Beta22. My Beta22 is a simple 2 board built with a separated Sigma22, but they weight 10lb+ easily.
           I bought AND KEPT O2 because:
          1) O2 does not sound far less than my previous AMB M3 (based on memory only, sorry can not offer impression between O2 vs M3. But based on side-by-side comparison, my ears did prefer Beta22 over M3 overall and especially in terms of soundstage, musical immersion and refinement);
          2) O2 is transportable (i.e., fits in my jean pocket) and drives LCD-2s sufficiently when I need a clean portable amp around my house. O2 is cheap but good enough to be my secondary rig outside of my man cave (which has Beta22).
          3) O2 can be used as a battery-powered pre-amp that is free of noise (e.g., no ground loop), if you do not mind using adapters. O2 drives my FirstWatt F2 clone beautifully without any noise. By contrast, I had to have my M3 modified to work as a pre-amp (M3's stock gain 11X and ground loop caused noise).
  6. stv014

    It should not be worse in theory than the Mini3, quite the opposite in fact.
  7. zzffnn
    I did Not mean Mini3. No one here use M3 to represent Mini3.
    I was just too lazy to type MMM or M^3. I meant M^3 with Sigma11. Not Mini3 with some batteries.
  8. 2000impreza


    Interesting comparison between the Objective 2 against the Beta22 and the bit on the M3 at the end. I have been considering putting together a M3 to see how it stacks up against the Objective 2. The Beta 22 seems like quite a step up from the Objective 2. I would imagine the future up coming desktop version of the O2(ODA) would better compete against it.
  9. zzffnn
    @ 200impreza,
    I suggest that you build both M3 and O2 and decide for yourself.
    M3 may sound better than O2. I just can not remember it as I did not have O2 and M3 side by side.  When I had M3 and Beta22 side by side, M3 did not impress me enough sonically for me to keep it. Utility wise, M3 is the same as Beta22 (not portable).
    While O2 can not compete with Beta22 in sonic performance either, its portability attracts me enough to keep it.
    I do not know if ODA would be better if its power supply section is not improved further.
  10. mikeaj
    With this design, as has been established earlier (I'm skipping the details here), an improvement in the power supply shouldn't make a difference in the sound.
    That said, ODA should have a different power supply scheme, so the power supply performance could be improved.  Actually, a different PCB and layout probably could potentially improve performance more than a change of power supply, and the ODA will have that as well.  Maybe the hotter components will be moved away from the electrolytic capacitors, which could improve their lifespan from maybe a decade or two, to more decades.  Anyway, the key point is that the designer doesn't even expect the ODA to sound different than the O2, unless I've misinterpreted things, so I wouldn't hold off on the ODA expecting it to be much better from a sound quality point of view.  I don't expect all listeners to agree though, so it'll be interesting to see what peoples' impressions are.
    The more interesting thing is the ODAC I think.  And that fits into the O2 default enclosure if you remove the batteries, as well as the ODA, but of course it can be used as a standalone DAC too.  Anybody planning to get an ODAC?  (I probably won't.)  Are you willing to give up on the batteries?  I rarely make use of the battery operation, but maybe others use it much more.  I guess the ODAC will need its own thread when the time comes.
  11. zzffnn
    I guess I would wait for a portable O2 with an integrated ODAC that takes USB, optical and coaxial inputs (in other words, something better than Fiio E17). The current ODAC takes USB only. The designer is surely right in that more people use computer as source, thus a good USB dac would be more helpful.
    However, there are also people (like me) who wants coaxial and optical dacs to work with CD players, Squeezebox and PS3. The benefit of being portable is that you may only need one for your entire house (as opposed to multiple rigs for multiple rooms). Desktop rigs surely sound better than portables;  however when you have a good desktop rig already, you may not want to spend that much more for a 2nd or 3rd rig.
  12. Draygonn

    I'm planning on getting an ODAC for my secondary rig, placing it inside the Crack's enclosure. I haven't used the O2's batteries yet but I'll try out the O2/Thunderpants combo on my next cross country flight.
  13. upstateguy


    Sounds to me like your B22 is coloring the sound a bit, boosting the bass and depressing the treble.  My O2 sounds like a less powerful GS-1 while my M^3 sounds like a less powerful beta. 
    Both the O2 and the GS-1 have a greater transparency more resolution than the M^3, which interestingly, colors the sound in the same way your beta does.
    I haven't compared the GS-1 with a beta in a while but when I did, I felt the GS-1 was cleaner and more transparent and the Beta more powerful and capable of higher volumes.

  14. Negakinu


    Obtained an O2 through a great friend of mine and he's shipping it to me as we speak. It's the JDS Labs build. Can't wait to get my grubby paws on it and dirty fingerprints all over it. 
  15. zzffnn
    @ upstateguy

    Your sound description may be absolutely right if it is in relative terms. Some times it is really hard to say what is neutrality as opposed to coloration.

    I guess it is more of a preference thing. One person’s definition of “coloration” may be another person’s “neutrality”, just like one person’s “greater transparency / more resolution” may be another person’s “brightness coloration”.

    I am quite sure GS-1 and Beta22 will reveal similarly impressive measurements (e.g., frequency response and slew rate, ect). Still, one individual may prefer Beta22 because of 100 factors, 50 of which may not applied to another individual.

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